The incorporation of electronic devices with tire structures has been shown to yield many practical advantages. Piezoelectric devices have been incorporated with tire patches to provide a power source to various sensors and other components of a tire patch used to measure tire parameters. Piezoelectric devices have also been used to acquire data about various physical parameters of a tire during rotation of the tire. Such information may be useful in tire monitoring and warning systems as well as in tire testing and design.
One known structure for a piezoelectric device includes a substrate having one or more piezoelectric components, such as a power generation component and a signal generation component. Each piezoelectric component can include a sandwich structure that includes a top conductive layer and a lower conductive layer that sandwich a piezoelectric layer. The substrate can include various insulating layers, such as a top insulating layer and a bottom insulating layer to protect and insulate the piezoelectric components. The various piezoelectric components of the piezoelectric device can be electrically coupled to an external device, such as a printed circuit board, using conductive terminals.
In typical connections for the piezoelectric device, the conductive terminals for the piezoelectric components of the substrate are all located proximate to and are exposed to a single surface of the substrate, such as a top surface of the piezoelectric substrate. In these connections, an electrical connection is made between the conductive terminal located proximate to the top surface of the piezoelectric substrate and a lower conductive layer using a compression connection. This compression connection involves bringing a conductor proximate the top conductive layer in communication with the conductive terminal and a conductor in communication with the lower conductive layer using locally applied high pressure compression techniques to create electrical contact between the conductive terminal and the lower conductive layer.
For example, FIG. 1 depicts an exemplary piezoelectric device 10 having a known connection structure 30. As shown, the connection structure 30 includes a plurality of conductive terminals 32, 34, 36, 38. Each of the conductive terminals 32, 34, 36, and 38 is exposed to the same surface of the piezoelectric device 10 through the same insulating layer 40 of piezoelectric device 10. Certain of the conductive terminals 34 and 36 are coupled to piezoelectric components in the piezoelectric device 10 through compression connections 50. The compression connections 50 require a conductor disposed in one layer of the piezoelectric device 10 to be brought into contact with a conductor disposed in another layer of the piezoelectric device 10 through high pressure compression. As depicted, the space required for compression connections 50 can take up valuable real estate on the piezoelectric device 10.
Given the strain that a piezoelectric device can be subjected to during rotation of a tire, a compression connection coupling a conductive terminal to a lower conductive layer in a piezoelectric device can be disrupted or can fail during use of the piezoelectric device. In addition, in many applications, a relatively rigid material, such as FR4, is used for the insulating layers of the substrate. It can be difficult to create workable compression connections through these rigid insulating layers using locally applied high pressure compression techniques.
Thus, a need exists for an improved electrical connection structure for a piezoelectric device. A connection structure that readily allows for incorporation of the piezoelectric device into a tire patch would be particularly useful.